'No one could have foreseen bridge problem,' says Arup

Engineer accepts blame for swaying but says British Standards for bridges will need to be rewritten.

Engineers at Ove Arup & Partners believe that the problems encountered by the Millennium Bridge will lead to a “complete rewriting” of the British Standard for suspension bridges.

Ove Arup is keen to counter criticism of the problems that led to Techniker director Matthew Wells calling the footbridge an “engineering tragedy”.

Structural engineer Roger Ridsdill Smith, who worked on the bridge from its conception, conceded that the blame for the problems rested with Ove Arup.

However, he added: “The current movement in the bridge is unacceptable, but no one could have foreseen the problems that are affecting the structure. I believe the issues surrounding the swaying in the bridge will lead to a complete rewrite of the guidance relating to suspension bridges.”

The current British Standard for suspension bridges was published in 1978 and last amended in 1983.

Ridsdill Smith also hit back at suggestions that Ove Arup had got its sums wrong in its design work for the bridge.

I believe the swaying will lead to a complete rewrite of guidance on suspension bridges

Roger Ridsdill Smith, Ove Arup

He said: “Two separate teams within Ove Arup looked at the project in isolation from one another and came up with the same figures. The scheme was then independently examined by Mott MacDonald. Nobody could have guessed that there would be swaying of this sort.”

Ove Arup is currently looking at a number of issues that could be causing the excessive swaying that forced the Millennium Bridge Trust to close the crossing last week.

It has also emerged that the footbridge may have to remain closed until November.

One line of inquiry into the causes of the problem is looking at the interaction of the different materials in the bridge.

These materials, which include aluminium and steel, each have different loading qualities; that is, they respond differently to pressure. Aluminium is less rigid than steel and vibrates more.